To be fair. The massdrop offering includes the following items that you don't get for that $349 mother's day sale price: grill cover, tote bag, two rubs, two sauces, and two 8-pound bags of grill pellets. The grill cover and tote bag MSRP at about $50 each.
If you don't want those, you're definitely better off picking it up from a dealer while the mother's day sale is going on. (GMG does not sell direct, you have to buy it from a dealer)
This massdrop is also convenient for those that don't have a dealer nearby.